System and method for controlling a system that includes variable speed compressor

ABSTRACT

A system and method for controlling a system that includes a variable speed compressor are described. The method can provide improved accuracy in the control of a system, for example, a heating, ventilating, and air condition (HVAC) system that includes a variable speed compressor, and can reduce a compressor cycling frequency of the compressor when a required capacity is below a minimum capacity of the compressor.

The embodiments disclosed herein relate generally to a system and methodfor controlling a system that includes at least one variable speedcompressor.

BACKGROUND

Generally, certain factors such as a minimum operating speed arerequired for prolonging the life of a variable speed compressor. Suchrequirements can affect energy efficiencies. Improvements in control ofsystems that include a variable speed compressor are desirable.

SUMMARY

The embodiments described herein are directed to a system and method forcontrolling a system that includes for example at least one variablespeed compressor. The method can provide improved accuracy in thecontrol of a system, for example, a heating, ventilating, and aircondition (HVAC) system that includes at least one variable speedcompressor, and can reduce a compressor cycling frequency of thecompressor when a required capacity is below a minimum capacity of thecompressor.

Generally, the improved accuracy and reduction in compressor cyclingfrequency are achieved by simultaneously controlling the variable speedcompressor and a supply fan that are included in the system. The systemand method described herein can advantageously lead to improved energyefficiencies. That is, in general, cycling between startup and shutdowncan not only help prolong the life of the compressor, but also canimprove energy efficiencies. The system and method described herein alsocan lead to a higher percentage latent capacity for improved spacedehumidification so that an additional reheating of the supply air whichis typically conducted by traditional air-side products fordehumidification is not required.

In general, a different fan speed and compressor speed combination canprovide the same unit or required capacity. The system and methoddescribed herein can determine the fan speed from the current compressorspeed based on predetermined equations or maps. An energy efficiencyequation/map can be setup so that the system will achieve maximum energyefficiency when provided the same unit or required capacity.

In some examples, the dehumidification map can have a lower fan speedthan the energy efficiency map does when the same compressor speed isused. In this instance, controlling based on the dehumidificationequation/map can remove more moisture and improve spacedehumidification. In some instances, the controller can choose to runbased on an energy efficiency map when space humidity is not high and torun based on a dehumidification map when space humidity is too high.

In some embodiments, the system includes a variable speed compressor, acondenser, an evaporator, and a supply fan. In some examples, the systemcan further include a controller that is configured to control thesystem by executing a control program or algorithm that is stored in amemory of the controller. In some examples, the controller is configuredso that the variable speed compressor can operate in four differentoperational states: a unit off state, a startup state, a running stateand a shutdown state.

In the unit off state, the variable speed compressor stays off at theoff position so that the speed of the variable speed compressor is at 0revolutions per second (rps). In some instances, the fan also can be offso that the speed of the fan is at 0 rps.

In the startup state, the speed of the variable speed compressor canramp up at a constant rate from 0 rps until the speed reaches a startupspeed of the compressor. In some instances, the fan can run at a minimumspeed.

In the running state, the variable speed compressor is modulated betweena minimum speed and a maximum speed. In some instance, the fan also canbe modulated between a minimum speed and a maximum speed.

In the shutdown state, the variable speed compressor can ramp down fromthe minimum speed to 0 rps. The shutdown is complete when 0 rps isreached. In some instances, the fan can run at a minimum speed.

In one embodiment, the algorithm that is executed by the controllerincludes determining a required capacity and comparing the determinedrequired capacity with a minimum capacity of a variable speedcompressor.

If the determined required capacity is greater than the minimum capacityof the variable speed compressor, then the variable speed compressoroperates in the running state.

If the determined required capacity is less than the minimum capacity ofthe variable speed compressor, then the variable speed compressor willcycle between the four different operating states based on thedetermined required capacity.

Other aspects of the invention will become apparent by consideration ofthe detailed description and accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Referring now to the drawings in which like reference numbers representcorresponding parts throughout.

FIG. 1 is a schematic illustration of a system for controlling avariable speed compressor and a supply fan, according to one embodiment.

FIGS. 2A and 2B are flow charts of the overall processes involved incontrolling the variable speed compressor, according to one embodiment.

FIG. 3 shows a schematic representation of the cycling process,according to one embodiment.

FIG. 4 shows a block diagram of a feedback control system using a PIcontroller, according to one embodiment.

FIG. 5 shows a graph of how the speeds of the supply fan and thecompressor are modulated simultaneously, according to one embodiment.

DETAILED DESCRIPTION

The embodiments described herein are directed to a system and method forproviding control in a system that includes a variable speed compressor.The system can be any system that utilizes a variable speed compressor,including water source heat pumps, unitary equipment, air handlers andterminal units.

FIG. 1 provides a schematic illustration of one embodiment of thedisclosed system (see system 100 in FIG. 1). The system 100 includes aconditioned space 104 and a ductwork 113 that is in fluid communicationwith the conditioned space 104. The term “conditioned space” hereinmeans a single space or a group of spaces, where the single space or thegroup of spaces can be defined as a zone or zones. The conditioned space104 can include a thermostat 119 that measures a dry-bulb temperature ofthe conditioned space 104. The term “dry-bulb temperature” herein meansa temperature of air measured by the thermostat 119 that is freelyexposed to the air but shielded from radiation and moisture.

The ductwork 113 can include a cooling coil 126 and a supply fan 131.The ductwork 113 can include other components that are typicallyincluded in a HVAC system, including a relief fan (not shown). Theductwork 113 and the conditioned space 104 can be configured so thatneeded airflow can flow from the ductwork 113 into the conditioned space104, back into the ductwork 113 and then out of the ductwork 113 asgenerally known in the art.

Generally, air flows past the cooling coil 126 so as to be cooled. Thecooled air then is delivered by the supply fan 131 into the conditionedspace 104 as supply air. The supply fan 131 also can be used to draw airout of the conditioned space 104 as return air. Some outdoor air forventilation can be mixed with the recirculated portion of the returnair. The remaining return air, that which has been replaced by outdoorair, can be then exhausted as exhaust air by a relief fan.

In some examples, the cooling coil 126 can be in fluid communicationwith a condenser 142 and a compressor 137. In FIG. 1, the system 100 isillustrated as having one compressor, but it is to be realized that morethan one compressor can be used. In the instance where more than onecompressor is used, the compressors can operate, for example, parallelto one another.

In one example, the compressor 137 is a variable speed compressor. Theterm “variable speed compressor” means a compressor whose speed can becontrolled, for example, by a controller, as generally understood in theart. The variable speed compressor 137 can include components that aregenerally known in the art, including a variable speed drive and amotor. The speed of the compressor 137 is generally controlled bycontrolling the speed of the motor that is driven by the variable speeddrive. The variable speed compressor 137 can be any compressor type thatis suitable for use in a HVAC system, and can include, but is notlimited to reciprocating, scroll, rotary, screw, centrifugal, etc. It isto be realized that some deviation or enhancements may be requireddepending on the type of compressor used, e.g., for a screw orcentrifugal compressor.

The variable speed compressor 137 generally functions to compressrefrigerant gas and feed the resulting high-pressure andhigh-temperature refrigerant gas to the condenser 142. As is generallyunderstood in the art, a capacity of the variable speed compressor 137is based on the operating speed of the variable speed compressor 137.That is, the capacity of the variable speed compressor 137 willgenerally increase as compressor speed increases when other variables inthe system stay the same. In the description that follows, a variablespeed compressor will be described. However, it is to be realized thatthe concepts herein can apply to any suitable modulating capacitycompressor. Note that a variable speed compressor is understood to be anexample of a modulating capacity compressor. The other variables mayinclude condenser fan speed, condenser ambient conditions and evaporatorentering air conditions.

Generally, the variable speed compressor 137 has a minimum capacity. Theterm “minimum capacity of the variable speed compressor 137” means thelowest operating speed or capacity of the variable speed compressor 137necessary to prevent damage to the variable speed compressor 137. Thatis, in general, as the load of a variable speed compressor decreases,the compressor becomes less efficient, which can lead to increasedinternal compressor temperatures. This can in turn lead to overheatingof the rotor temperature and the radial expansion or radial growth ofthe rotors. This radial growth can result in a radial rub with thecompressor housing, subsequently causing a failure. Also, damage canresult from a lack of compressor lubrication at lower operating speeds.The minimum capacity of the variable speed compressor 137 is the lowestoperating speed or capacity of the variable speed compressor 137necessary to prevent such failure of the variable speed compressor 137.It is to be appreciated that the minimum capacity of the variable speedcompressor 137 can be determined and/or set by a user.

In some instances, the minimum capacity of the variable speed compressor137 is dependent on factors such as the type of variable speedcompressor 137 used. In some examples, the minimum capacity of thevariable speed compressor 137 is predetermined, e.g., by themanufacturer of the variable speed compressor 137. In some otherexamples, the minimum capacity of the variable speed compressor 137 isset by a user. In some other examples, the minimum capacity of thevariable speed compressor 137 can be calculated in a manner that isgenerally known in the art, e.g., based on readings from a temperaturesensor 169 of the fluid that is discharged from the compressor 137and/or a temperature sensor 172 of the compressor 137.

The cooling coil 126, the condenser 142 and the compressor 137 canutilize a refrigeration cycle that is generally known in the art. Insome instances of the refrigeration cycle, the variable speed compressor137 can feed high-pressure and high-temperature refrigerant gas to thecondenser 142. The refrigerant vapor that is delivered to the condenser142 then can enter into a heat exchange relationship with a fluid, forexample, air. The condensed liquid refrigerant from the condenser 142then can flow through an expansion device (not shown) to an evaporator132. A secondary liquid, e.g., water, that has flowed into theevaporator 132 then can enter into a heat exchange relationship with thelow pressure/low temperature liquid refrigerant to chill the temperatureof the secondary liquid. The chilled secondary liquid can then runthrough the cooling coil 126, and the refrigerant liquid in theevaporator 132 can undergo a phase change to a refrigerant vapor as aresult of the heat exchange relationship with the secondary liquid. Therefrigerant vapor then can return to the variable speed compressor 137to complete the refrigeration cycle.

The system 100 further can include a controller 175. The controller 175generally can include a processor, a memory, a clock and an input/output(I/O) interface and can be configured to receive data as input fromvarious components within the system 100, and send command signals asoutput to various components within the system 100.

In some examples, during operation, the controller 175 can receiveinformation, for instance, from the variable speed compressor 137, thesupply fan 131, the thermostat 119, the temperature sensor 169, and/orthe temperature sensor 172 through the I/O interface, process thereceived information using the processor based on an algorithm stored inthe memory, and then send command signals, for instance, to thecomponents involved in the refrigeration cycle including the compressor137 and/or the supply fan 131. For example, the controller 175 canreceive information regarding the dry-bulb temperature from thethermostat 119 and the current operating speed of the variable speedcompressor 137, process the data, and then based on the data, send acommand signal to the variable speed compressor 137 so as to control thespeed of the compressor 137. It is to be realized that the controller175 can be configured to receive information and send command signals toother components that are generally known to be included in a systemthat utilizes a variable speed compressor.

Details of the various algorithms that can be stored in the memory willnow be provided below.

Generally, the controller 175 can be configured to implement thedisclosed method of controlling the system 100 as illustrated in FIGS.2A and 2B. In general, the processes described in FIGS. 2A and 2B areexecuted by the processor executing program instructions (algorithms)stored in the memory of the controller 175. The process can be initiatedat any time during the four different operating states of the variablespeed compressor 137. In some examples, the process can be initiatedmanually by a user, or initiated automatically, for example, by apreprogrammed instruction stored inside the memory.

With reference to FIG. 2A, in one embodiment, the disclosed method oralgorithm 200 initiates at step 106 and proceeds to step 109 where adetermination is made as to a required capacity of the conditioned space104. The term “required capacity” means a capacity or speed of thevariable speed compressor 137 that is necessary to achieve apredetermined temperature and/or a predetermined relative humidity.

The determination of the required capacity can involve the use ofcertain parameters and calculations that are generally known in the art.For instance, the determination of the required capacity can be based ona prediction algorithm that involves calculations using a currentreading of a dry-bulb temperature of the thermostat 119 and apredetermined temperature of the conditioned space 104. Thepredetermined temperature may be a temperature of the conditioned spacethat is desired by a user. The predetermined temperature may be manuallyset by a user, e.g., as input to be processed by the controller 175.

In one example, a PI controller can be used to determine the requiredcapacity. In this instance, when the space temperature is above a setpoint, the PI controller will increase the capacity value, and when thespace temperature is below the set point, the PI controller willdecrease the capacity value. The adjustment will continue until thetemperature reaches set point. The final capacity value is the “requiredcapacity”. In one example, passive dehumidification is employed. In thisinstance, when relative humidity is high, a dehumidification map is usedto coordinate the fan and the compressor, which will remove moremoisture from conditioned air. The required capacity is calculated inthe same manner as described above.

After step 109, a determination is made as to whether the requiredcapacity is larger than a minimum capacity of the variable speedcompressor 137. In some examples, the minimum capacity of the variablespeed compressor 137 can be predetermined. In some other examples, theminimum capacity of the variable speed compressor 137 can be set by auser, e.g., as an input to be processed by the controller 175. In someother examples, the minimum capacity of the variable speed compressor137 can be calculated by the controller 175 in a manner that isgenerally known in the art, e.g., based on readings from a temperaturesensor 169 of the fluid that is discharged from the compressor 137and/or a temperature sensor 172 of the compressor 137.

If the required capacity is the same as the minimum capacity, then thevariable speed compressor 137 will remain at the minimum speed.

If the required capacity is less than the minimum capacity, then thealgorithm proceeds to a cycling process {circle around (1)} (furtherdescribed/illustrated in FIG. 3). In some examples, conducting thecycling process {circle around (1)} based on the comparison between thedetermined required capacity and the minimum capacity can lead toimprovement in space comfort control accuracy and reduction ofcompressor cycling frequency as compared to those of dead band basedcycling by anticipating the load requirement and its dynamic changes.One example of dead band based cycling is when the space temperature is1° F. above the set point, the compressor is turned on, and when thespace temperature is 1° F. below the set point, the compressor is turnedoff.

In one example, the load requirement and its dynamic changes isanticipated by the PI controller, for instance, using the currenttemperature and the previous temperature to calculate the requiredcapacity, and accordingly, taking the change in speed into considerationto predict what may happen in the future.

An overview of the cycling process {circle around (1)} is illustrated inFIG. 3. Generally, the cycling process {circle around (1)} involvescycling between four different operational states: operating in a unitoff state 202, operating in a startup state 207, operating in a runningstate 212 and operating in a shutdown state 218.

In the unit off state 202, the variable speed compressor 137 stays offat the off position so that the speed of the variable speed compressor137 is at 0 revolutions per second (rps). In some instances, the supplyfan 131 also can be turned off so that the speed of the fan 131 is at 0rps. In some examples, the supply fan 131 is turned off unless it is onfan off delay. “Fan off delay” means that the fan will not turn offuntil the compressor is turned off for a predetermined amount of time,e.g., about 30 seconds.

In the startup state 207, the speed of the variable speed compressor 137can ramp up at a constant rate from 0 rps until the speed reaches astartup speed of the compressor 137. In some examples, the constant ratecan be predetermined. In one implementation, the constant rate is anincrease of about 2 revolutions per second. It is to be realized thatthe constant rate can vary depending on the allowable speed defined bythe system components and the compressor specification. In otherexamples, the constant rate can be determined based on the requiredcapacity determined in step 109 at FIG. 2. In some examples, thevariable speed compressor 137 will ramp up at a constant rate from 0 rpsuntil a startup speed of 25 rps, which is 25% of the maximum speed of100 rps, is reached. Note that both the minimum and maximum speed valuescan vary depending on the allowable speed defined by the systemcomponents and the compressor specification. In some examples, after thestartup speed is reached, the compressor 137 will operate at the startupspeed for a predetermined amount of time. In some implementations, thepredetermined amount of time is about 120 seconds.

In some instances in the startup state 207, the supply fan 131 can runat a minimum speed where a variable speed fan is used for the supply fan131.

In the running state 212, the variable speed compressor 137 is modulatedbetween a minimum speed and a maximum speed. In some examples, theminimum speed is a function of entering water temperature (EWT) of thecondenser. In some instances, the fan 131 also can be modulated betweena minimum speed and a maximum speed.

In the shutdown state 218, the variable speed compressor 137 can rampdown from the minimum speed to 0 rps. Shutdown is complete when 0 rps isreached. In some instances, the fan can run at a minimum speed.

The algorithm of the cycling process {circle around (1)} is illustratedin FIG. 2B. The cycling process {circle around (1)} initially involvesdetermining the operating state of the variable speed compressor 137(step S100). The operating state of the compressor 137 can be determinedto be in the unit off state 202, startup state 207, running state 212 orshutdown state 218. Note that at power-up, the controller 175 will startfrom the off state and use the logic in FIG. 2B to determine the nextoperating states.

If the operating state of the compressor 137 is determined to be in thestartup state 207, then a determination is made as to whether startup iscompleted (step 220).

In some examples, startup is completed when the speed of the variablespeed compressor 137 reaches the startup speed of the compressor 137.

If startup is determined to be incomplete, then the algorithm goes backto startup 207. If the startup is determined to be complete, then thealgorithm goes to step 228.

In step 228, a determination is made as to whether the required capacitydetermined in step 109 is greater than 0. If the required capacity isgreater than 0, then the algorithm proceeds to operating the compressor137 in the running state 212. If the required capacity is equal to zero,then the compressor 137 proceeds to operate in the shutdown state 218.

Note that in some examples, the algorithm can involve the step ofdetermining whether the required capacity determined in step 109 isgreater than 0 before the step of determining whether startup iscompleted. In this instance, the outcome would be the same as conductingthe steps 220 and 228 in that order as described above. For example, ifthe required capacity is determined to be 0 at the running state, thealgorithm goes to the shutdown state 218. If the required capacity isdetected to be 0 at the startup state, then the algorithm goes to theshutdown state 218 as well.

If the operating state of the compressor 137 is determined to be in therunning state 212, then the algorithm proceeds to step 235 where a timecalculation is made. In one example, the time calculation involvescalculating an amount of time the compressor will be turned on. In oneinstance, the time calculation is based on the required capacitycalculated in step 109.

After step 235, a timer comparison is made (step 242). In this step, thetime that the compressor will be turned on as determined in step 235 iscompared with the current time, and the compressor is turned on for anamount of time based on the comparison.

After the compressor 137 is turned on for the determined amount of time,the compressor 137 then operates in the shutdown state 218.

If the operating state of the compressor 137 is determined to be in theshutdown state 218, the algorithm proceeds to step 254 where adetermination is made as to whether shutdown is complete. In oneexample, shutdown is complete when the speed of the compressor reaches 0rps. If shutdown is determined not to be complete, then the algorithmreturns to the shutdown state 218. If shutdown is determined to becomplete, then the compressor 137 proceeds to operate in the unit offstate 202.

If the operating state of the compressor 137 is determined to be in theunit off state 202, then the algorithm proceeds to step 265 where a timecalculation is made. In one example, the time calculation involvescalculating an amount of time the compressor will be turned off. In oneinstance, the time calculation is based on the required capacitycalculated in step 109.

After step 265, a timer comparison is made (step 272). In this step, thetime that the compressor will be turned off as determined in step 265 iscompared with the current time, and the compressor is turned off for thedetermined amount of time.

After the compressor 137 is turned off for the determined amount oftime, the compressor 137 then proceeds to operate in the startup state207.

Referring back to step 114 in FIG. 2A, if the required capacity isgreater than the minimum capacity, then the algorithm proceeds to step121, where the compressor 137 operates in the running state 212, andthen proceeds to step 135 where a time calculation is made. In oneexample, the time calculation involves calculating an amount of time thecompressor will be turned on. In one instance, the time calculation isbased on the required capacity calculated in step 109.

After step 135, a timer comparison is made (step 145). In this step, thetime that the compressor will be turned on as determined in step 135 iscompared with the current time, and the compressor is turned on for thedetermined amount of time.

In some examples, a feedback control system using a PI controller can beused to calculate the required capacity as in step 109, execute the timecalculation as in steps 135, 235 and 265, and execute the timercomparison as in steps 145, 242 and 272. A block diagram of a feedbackcontrol system 380 using a PI controller 402 is illustrated in FIG. 4.

The PI controller 402 can receive as input a current reading of adry-bulb temperature of the thermostat 119 and a predeterminedtemperature of the conditioned space 104. The predetermined temperaturemay be a temperature of the conditioned space 104 that is desired by auser. The PI controller 402 then can be used to calculate the requiredcapacity, and provide as a controller output if there is a disparitybetween the current reading of a dry-bulb temperature of the thermostat119 and the predetermined temperature of the conditioned space 104. Thecontroller output then can be used for calculating the amount of timethe compressor needs to be turned on or off (block 405) as in steps135/235 and 265, respectively, make a timer comparison (block 411) as insteps 145, 242 and 272, and turn the compressor 137 on or off for thedetermined amount of time.

In one example, the speed of the supply fan 131 can be modulated at thesame time as the speed of the compressor 137. In one instance, thesupply fan 131 is a variable speed fan. In this instance, the fan speedincreases or decreases with the compressor speed following apredetermined map(s). In some examples, the predetermined map(s) is anenergy efficiency map(s) and/or a dehumidification map(s). In oneexample, the “energy efficiency map” and “dehumidification map” arelookup tables where the fan speed is calculated based on the compressorspeed. Generally, there are many combinations of fan speed andcompressor speed that can provide the same capacity. The energyefficiency map will provide the best overall energy efficiency, whilethe dehumidification map will provide the best moisture removalperformance. In some instances, the fan speed will be lower in thedehumidification map than in the energy efficiency map when the samecompressor speed is required.

In some examples, the energy efficiency map is a compressor efficiencymap as described in U.S. Pat. No. 5,537,830, which is hereinincorporated by reference.

In some examples, the predetermined map(s) coordinate the speeds of thefan 131 and compressor 137. In some instances, the predetermined map(s)are different for the heating mode and the cooling mode. In one example,the heating and cooling mode transition is determined by the controller175. For example, heating is enabled when the space temperature staysbelow a set point for an extended period of time, while cooling isenabled when the space temperature stays above a set point for anextended period of time.

In other instances, the predetermined map(s) can change based onoperating conditions such as the entering water temperature for awater-source unit. In this instance, the system 100 would furtherinclude a sensor (not shown) for the entering water for the water-sourceunit. In yet some other instances, the predetermined map(s) includes adehumidification map. In some implementations, the dehumidification maphas a lower fan speed to provide a higher percentage of latent capacityfor improved space dehumidification. In one example, with the samecompressor speed and the same entering air condition, the lower fanspeed can result in a lower discharge air temperature and a lowersaturate humidity. As such, a humidity ratio of the discharge air can bedecreased.

In another instance, the supply fan 131 is a fixed speed fan. In thisinstance, the supply fan 131 is turned on or off at the same time thespeed of the compressor 137 is modulated. In one instance, the fan 131is turned on or off for a certain amount of time depending on thepredetermined map(s) described above. In one example, the fan will beturned on when the compressor is on, and the fan will be turned offafter the compressor is turned off for a period of fan off delay.

One example of how the speed of the supply fan 131 can be modulated atthe same time of the speed of the compressor is illustrated in FIG. 5.FIG. 5 depicts a graph, where the x-axis of the graph represents therequired capacity and the y-axis of the graph represents the speeds ofthe supply fan 131 and the compressor 137. In the graph, region “a”represents the startup state 207 and region “b” represents the runningstate 212.

In the example shown in FIG. 5, during the startup state 207, thecompressor 137 ramps up speed at a constant rate from 0 rps to a minimumspeed of the compressor 137. During this time period, the supply fan 131runs at a certain minimum speed. After the compressor 137 reaches itsminimum speed, the compressor 137 enters the running state 212, wherethe compressor 137 continues to ramp up speed at a constant rate. At thepoint where the compressor 137 reaches its minimum speed and enters therunning state 212, the fan 131 begins to increase in speed together withthe speed of the compressor 137. The speeds of the fan 131 andcompressor 137 increase together at a constant rate until a maximumspeed for the fan 131 and a maximum speed for the compressor 137 arereached.

Aspects

-   Any of aspects 1-8 can be combined with any of aspects 9-14. Any of    aspects 1-8 can be combined with aspect 15. Any of aspects 1-8 can    be combined with aspect 16.    -   Aspect 1. A system, comprising:        -   a compressor having the following operational states: a unit            off state, a startup state, and a running state, and        -   a controller that is configured to        -   (a) determine a required capacity of a conditioned space;        -   (b) compare the required capacity determined in (a) with a            minimum capacity of the compressor,        -   wherein if the required capacity determined in (a) is            greater than the minimum capacity of the compressor, then            -   (c1) operate the compressor in the running state; and        -   wherein if the required capacity determined (a) is less than            the minimum capacity,            -   (c2) cycle between each of the operational states based                on the required capacity determined in (a).    -   Aspect 2. The system of any of aspects 1 and 3-8, further        comprising a supply fan, wherein the compressor is a variable        speed compressor, and the supply fan and the variable speed        compressor are controlled simultaneously.    -   Aspect 3. The system of any of aspects 1-2 and 4-8, wherein        operational state of the compressor further comprises a shutdown        state, wherein in the unit off state, the compressor stays off        at the off position so that the speed of the compressor is at 0        revolutions per second (rps), wherein in the startup state, the        speed of the compressor ramps up at a constant rate from 0 rps        until the speed reaches a startup speed of the compressor,        wherein in the running state, the compressor is modulated        between a minimum speed and a maximum speed, and wherein in the        shutdown state, the compressor ramps down from the minimum speed        to 0 rps.    -   Aspect 4. The system of any of aspects 1-3 and 5-8, wherein in        the unit off state, the supply fan is off so that the speed of        the supply fan is at 0 rps, wherein in the startup state, the        supply fan operates at a minimum speed, wherein in the running        state, the supply fan is modulated between a minimum speed and a        maximum speed, and wherein the shutdown state, the supply fan        operates at a minimum speed.    -   Aspect 5. The system of any of aspects 1-4 and 6-8, wherein the        supply fan is a variable speed fan.    -   Aspect 6. The system of any of aspects 1-5 and 7-8, wherein the        supply fan operates at a fixed speed.    -   Aspect 7. The system of any of aspects 1-6 and 8, wherein in        (c2), a determination is made as to the operating state of the        compressor.    -   Aspect 8. The system of any of aspects 1-7, wherein in (a), the        required capacity is based on a current reading of a dry-bulb        temperature of the conditioned space and a predetermined        temperature of the conditioned space.    -   Aspect 9. A method of controlling a heating, ventilating and air        conditioning system that includes a compressor, the compressor        having the following operational states: a unit off state, a        startup state, and a running state, the method comprising        -   (a) determining a required capacity of a conditioned space;        -   (b) comparing the required capacity determined in (a) with a            minimum capacity of the compressor,        -   wherein if the required capacity determined in (a) is            greater than the minimum capacity of the compressor, then            -   (c1) operate the compressor in the running state            -   wherein if the required capacity determined (a) is less                than the minimum capacity of the compressor,            -   (c2) cycle between each of the operational states based                on the required capacity determined in (a).    -   Aspect 10. The method of any of aspects 9 and 11-14, wherein the        system further comprises a supply fan, wherein the compressor is        a variable speed compressor, and wherein the compressor and the        supply fan are controlled simultaneously.    -   Aspect 11. The method of any of aspects 9-10 and 12-14, wherein        the operational state of the compressor further comprises a        shutdown state, wherein in the unit off state, the compressor        stays off at the off position so that the speed of the        compressor is at 0 revolutions per second (rps), wherein in the        startup state, the speed of the compressor ramps up at a        constant rate from 0 rps until the speed reaches a startup speed        of the compressor, wherein in the running state, the compressor        is modulated between a minimum speed and a maximum speed, and        wherein in the shutdown state, the compressor ramps down from        the minimum speed to 0 rps.    -   Aspect 12. The method of any of aspects 9-11 and 13-14, wherein        in the unit off state, the supply fan is off so that the speed        of the fan is at 0 rps, wherein in the startup state, the supply        fan operates at a minimum speed, wherein in the running state,        the supply fan is modulated between a minimum speed and a        maximum speed, and wherein the shutdown state, the supply        operates at a minimum speed.    -   Aspect 13. The method of any of aspects 9-12 and 14, wherein in        (c2), a determination is made as to the operating state of the        compressor.    -   Aspect 14. The method of any of aspects 9-13, wherein in (a),        the required capacity is based on a current reading of a dry        bulb temperature of the conditioned space and a predetermined        temperature of the conditioned space.    -   Aspect 15. A method for controlling a compressor and a supply        fan in a heating, ventilating and air conditioning system,        wherein the compressor and the supply fan are controlled based        on an efficiency map and/or a dehumidification map.    -   Aspect 16. A system, comprising:        -   a variable capacity compressor having the following            operational states: a unit off state, a startup state, and a            running state, and        -   a controller that is configured to        -   (a) determine a required capacity of a conditioned space;        -   (b) compare the required capacity determined in (a) with a            minimum capacity of the compressor,        -   wherein if the required capacity determined in (a) is            greater than the minimum capacity of the compressor, then            -   (c1) operate the compressor in the running state; and        -   wherein if the required capacity determined (a) is less than            the minimum capacity,            -   (c2) cycle between each of the operational states based                on the required capacity determined in (a).

With regard to the foregoing description, it is to be understood thatchanges may be made in detail, especially in matters of the constructionmaterials employed and the shape, size and arrangement of the partswithout departing from the scope of the present invention. It isintended that the specification and depicted embodiment to be consideredexemplary only, with a true scope and spirit of the invention beingindicated by the broad meaning of the claims.

1-16. (canceled)
 17. A method for controlling a compressor and a supplyfan in a heating, ventilating and air conditioning (HVAC) system, themethod comprising: controlling, based on an input received by acontroller, the compressor and the supply fan based on adehumidification map.
 18. The method of claim 17, further comprising:calculating a speed of the supply fan based on a speed of the compressoraccording to the dehumidification map, wherein the dehumidification mapincludes a lookup table.
 19. The method of claim 17, wherein the supplyfan is a variable speed fan.
 20. The method of claim 19, furthercomprising: increasing or decreasing a speed of the supply fan with aspeed of the compressor based on the dehumidification map.
 21. Themethod of claim 17, wherein the dehumidification map is based on spacehumidity.
 22. The method of claim 17, wherein the dehumidification mapis different for a heating mode from the dehumidification map for acooling mode.
 23. The method of claim 17, wherein the supply fan is afixed speed fan.
 24. The method of claim 23, further comprising: turningthe supply fan on or off when a speed of the compressor is modulated.25. The method of claim 24, further comprising: turning the supply fanon when the compressor is on, and turning the supply fan off after thecompressor is turned off for a period of time.
 26. The method of claim23, further comprising: turning the supply fan on or off for a certainamount of time based on the dehumidification map.
 27. The method ofclaim 17, further comprising: during a startup state, running the supplyfan at a minimum speed of the supply fan.
 28. The method of claim 17,further comprising: during a startup state, ramping up a compressorspeed at a constant rate from 0 revolutions per second (rps) to aminimum speed of the compressor.
 29. The method of claim 28, furthercomprising: the compressor entering a running state after the compressorreaches the minimum speed of the compressor.
 30. The method of claim 29,further comprising: during the running state, continuing to ramp up thecompressor speed at the constant rate.
 31. The method of claim 29,further comprising: during the running state, increasing speeds of thesupply fan and the compressor together until a maximum speed for thesupply fan and a maximum speed for the compressor are reached.
 32. Amethod for controlling a compressor and a supply fan in a heating,ventilating and air conditioning (HVAC) system, the method comprising:controlling, based on an input received by a controller, the compressorand the supply fan based on a dehumidification map, controlling, basedon an input received by a controller, the compressor and the supply fanbased on an efficiency map, wherein a speed of the compressor in thedehumidification map is the same as a speed of the compressor in theefficiency map, and a speed of the supply fan in the dehumidificationmap is lower than a speed of the supply fan in the efficiency map.
 33. Asystem, comprising: a compressor having the following operationalstates: a startup state, and a running state; a supply fan; and acontroller configured to control the compressor and the supply fan in aheating, ventilating and air conditioning (HVAC) system, wherein thecompressor and the supply fan are controlled based on a dehumidificationmap.
 34. The system of claim 33, wherein the compressor and the supplyfan are further controlled based on an efficiency map, the efficiencymap and the dehumidification map include lookup tables where a speed ofthe supply fan is calculated based on a speed of the compressor.
 35. Thesystem of claim 33, wherein during a startup state, the controller isconfigured to control the supply fan at a minimum speed of the supplyfan, and the controller is configured to ramp up a speed of thecompressor at a constant rate from 0 revolutions per second (rps) to aminimum speed of the compressor.
 36. The system of claim 33, whereinduring the running state, the controller is configured to continue toramp up the speed of the compressor at the constant rate, and thecontroller is configured to increase speeds of the supply fan andcompressor together until a maximum speed of the supply fan and amaximum speed of the compressor are reached.